Developmental Response To Temperature In Asiatic Toad (Bufo Gargarizans)

Global climate change has become one of the important threats to biodiversity,studying the impacts of climate change on organisms and its adaptations is one of research hotspots,and temperature change is one of the main performance of climate change.The organism responds to temperature change by migration,or long-term adaptation or phenotypic plasticity.The amphibian has complex life history,limited migration ability,and high sensitivity to environmental change,and it is one of the serious threats to extinction,so it is necessary and suitable for studying the role of long-term adaptation and phenotypic plasticity in biological response to temperature changes.Bufo gargarizans is one of the important materials for amphibious study,due to its wide distribution range,large population,strong reproductive capacity and variable habitats.This paper sampled three different geographical populations of Bufo gargarizans,which was sequentially increased in the latitude of three geographical locations in Baoding City(BD),Hebei Province,Changchun City(CC),and Heilongjiang Province(HEB),and compared developmental differences,including developmental timing,body weight,snout-vent length,body width,tail length,hind leg length,and growth rate in different temperature with geographical populations and different population with temperatures by common garden experiments,to explore long-term adaptation,phenotypic plasticity patterns and their relationship,and try to understand the difference of morphologic of Bufo gargarizans caused by temperature change.The research results showed that:(1)With the increasing of latitude,the survival rate of populations decreased in turn(P<0.001)(the difference between CC and HEB populations was unsignificant at 21?);the developmental timing decreased at 21?(P<0.001),and then increased at 28?(P<0.001);the growth rate increased at 21?(P<0.001)(the difference in the average body weight growth rate of CC\HEB populations were unsignificant,P=0.359),and decreased at 28?(P<0.001);Body weight,snout-vent length and tail length decreased gradually(P<0.001)(the difference in tail length of CC/HEB populations were unsignificant at 21?,P=0.11;the difference in snout-vent length and tail length of BD\CC populations were unsignificant at 28?,P=1.769 and P=0.396,respectively);and the body width gradually increased(the difference of CC\HEB populations were unsignificant at 21? and 28?,P=0.515 and P=0.69,respectively).Taken together,Bufo gargarizans in the high latitude showed shorter developmental timing,smaller body size,and faster growth rate.(2)Compared with 21?,Bufo gargarizans at 28? had higher survival rate(P<0.001),(HEB population was not significant,P=0.558),and shorter developmental timing(P<0.001),and smaller body weight,snout-vent length,body width,and tail length(P<0.001)(snout-vent length of CC population was no significant,P=0.198),and a faster developmental rate(P<0.001).Among plasticity,body plasticity was not significant among population(P=0.552),and developmental timing,snout-vent length,body width and tail length showed extremely strong phenotypic plasticity(P<0.001),and the plasticity of the developmental timing decreased with the increasing latitude.It indicated that Bufo gargarizans would prefer to adjust the developmental timing to response the environmental change.As the latitude increasing,the plasticity of the developmental timing decreased which indicated that this may be an adaptation to greater temperature fluctuations in the high latitude.(3)According to the above research results,we found that the population developmental characteristics of Bufo gargarizans in high latitude and high temperature are consistent.Both showed that tadpole has shorter developmental timing,smaller body size,and faster growth rate.The developmental difference among populations may be the further evolution of plasticity within the population.Phenotypic plasticity was an important aspect of species adaptive evolution.(4)In addition,there was a significant positive correlation between developmental timing with body weight and snout-vent length(P<0.05).Body width,hind leg length and snout-vent length were allometric(P<0.05),and allometric index is less than 1.It indicated that the change of developmental timing during metamorphosis leaded to morphological changes of larvae,and individuals with longer developmental timing had larger body size.However,the growth rate of the body width and the hind leg length were shorter than the growth rate of the snout-vent length,so individuals of larger body size had a relatively narrow body width and a relatively short hind leg length.